The present invention relates to a device for locking in position an adjustable steering column, especially for a motor vehicle, and to a column assembly including such a device.
Some motor vehicles have, for several years already, been equipped with devices for adjusting the position of the steering wheel, which are intended to adapt the position of the latter to the morphology of the driver of the vehicle.
Thus the position of the column and therefore of the steering wheel is adjustable axially, and by pivoting.
In the state of the art, these adjustment devices include a column-support structure connected to the rest of the structure of the vehicle and including two flanges between which the column is arranged and means for locking the column in position by bringing the flanges together.
These locking means comprise, for example, a tie extending between the flanges, a first end of which bears on one of the flanges and a second end of which is connected to locking elements.
Various embodiments of these locking elements have been proposed.
Thus, for example, these locking elements may consist of a screw-nut system, a toggle joint system, or even a system with a cam connected to a manipulating lever.
Another embodiment of these locking means is described in document GB-A-2,113,164 in the name of FORD MOTOR COMPANY LIMITED.
This document in effect describes a device the general structure of which is in the form described previously and in which the locking elements comprise a stop member at the second end of the tie, an intermediate bearing member in contact with the other flange of the support structure and capable of being displaced axially on the tie, and a manipulating member arranged between the stop member and the intermediate bearing member, connected to a manipulating lever, and capable of being displaced rotationally in a plane which is perpendicular to the tie, between an active position for locking the column, and a retracted position for unlocking it.
The facing surfaces of the manipulating member and of the intermediate bearing member or of the stop member comprise, for one of them, at least one projecting part which is adapted to interact with an incline on the other, in order to space these two surfaces apart and therefore to space apart the corresponding locking elements in order to bring the flanges closer together to lock the column, when the manipulating lever is displaced.
In the embodiment described in this document, the projecting parts consist of bosses formed integrally with the manipulating member and the inclines are made on the intermediate bearing member.
However, this device exhibits a certain number of drawbacks as regards manipulating the lever.
In effect, it is understood that the greater the tightening of the column to be obtained, the greater the friction between these various locking elements and therefore the more difficult the manipulation of the lever.
Document FR-A-2,671,040 in the name of the Applicant Company proposes various solutions for solving these problems.
To this end, this document relates to a locking device as described previously, in which the said projecting part comprises a rolling member connected to the corresponding locking element.
Two rolling members may be arranged on the corresponding locking element, on either side of the tie, and may each be adapted to interact with a facing incline on the corresponding surface of the other element.
Advantageously, these rolling members are interposed between the manipulating member and the intermediate bearing member, and rolling-contact bearing elements are interposed between the stop member and the manipulating member.
According to a particularly advantageous embodiment described in this document, the or each rolling member interposed between the manipulating member and the intermediate bearing member, and the or each rolling-contact bearing interposed between the manipulating member and the stop member of the second end of the tie, are arranged in pairs in a single recess passing through the manipulating member, bearing one against the other, one projecting between the manipulating member and the intermediate bearing member and the other between the manipulating member and the stop member.
It is mentioned in this document that these members and these rolling-contact elements may consist of balls.
However, the various embodiments described in this document, although offering a certain number of advantages as compared with conventional devices, remain the source of friction and wear of components and in particular of the rolling members and rolling-contact elements, which over time is manifested by problems in operating the device.
Of course, these problems may be solved by using components which offer suitable mechanical strength characteristics, but this is often manifested in an increase in the costs of manufacturing the device.